1. Technical Field
The present invention relates to a lead pin for a printed circuit board and a printed circuit board using the same.
2. Description of the Related Art
In a PGA substrate, when a T-type lead pin is bonded to a pad on a package substrate by using an Sn95-Sb5 solder (melting point of 232 to 240° C.) having a melting point higher than that of an Sn96-Ag3.5-X based solder (melting point of 221° C. used when bonding IC chips.
The above-mentioned process is essential to prevent the pin from being separated when the IC chips are mounted on the package substrate. Generally, in order to minimize thermal impact applied to the package substrate, the above-mentioned process shortens the time when a soldering is maintained at a temperature of a melting point or more, such that the time of discharging bubbles in the soldering is insufficient. In this case, the soldering are in a non-uniform distribution state to cause a problem of biasing the lead pin due to a tension with the lead pin, thereby making it possible to degrade the pin pull strength.
Further, even though the above-mentioned bubbles do not cause any problems during the bonding of the lead pin, the IC chips are again heated during the mounting process of the IC chips, such that they can cause the defects of the pin.